Addition of fertilizer, restoration of habitat boost Kootenai River trout

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Two major Bonneville Power Administration projects are tending to the welfare of Kootenai River fisheries, which have been starved for more than attention since Libby Dam went online in 1972.

The success of the multiyear, multimillion dollar projects is easy to confirm with an Idaho fishing license and a fly rod. Trout, whitefish and suckers are bigger in the river’s Idaho stretch, and their numbers have increased.

Floating the river’s 55-mile project area, mostly upstream from Bonners Ferry, and scanning data from fisheries research is even more convincing.

Most obvious is the heavy construction at several project sites for the Kootenai River Habitat Restoration Project. Crisscrossed logs and root wads being planted in critical shoreline areas resemble barriers on a D-Day beach as they redirect river flows while stabilizing and regenerating shoreline habitat.

Not so apparent – except perhaps to anglers – are results from a trickle of fertilizer that’s been applied since 2005 to the Kootenai River near the Montana-Idaho border.

“In some ways it’s the same as adding nutrients to your garden,” said Charlie Holderman, project manager and fisheries biologist for the Kootenai Tribe. “Do it right, and you’ll get more and bigger tomatoes.”

Both projects are coordinated by the tribe in conjunction with numerous other agencies and groups. Costs are about $2 million a year for the first five years of habitat restoration and $200,000-$500,000 annually for the nutrient enrichment project and associated monitoring.

The Bonneville Power Administration funds the projects through its obligation to mitigate impacts hydropower projects have had on native fisheries.

The habitat project is geared primarily to reviving the river’s endangered white sturgeon, said Sue Ireland, the tribe’s Fish and Wildlife Program director. However, a wide variety of fish and wildlife will benefit from the structures, rocks, willow plantings and other work to help naturalize a river with a hydrograph severely disrupted by operations at Libby Dam.

“Our funding seeks to help the ecosystem in a holistic way rather than just dumping a bunch of water out (of Lake Koocanusa) and seeing if it helps sturgeon,” she said.

The first habitat structures went in last year. They passed the first big test this spring, standing up to flood-stage flows, Ireland said.

The habitat effort started in 2001, with U.S. Geological Survey research on flow velocities and sediment transport. The tribe started planning the project four years before bringing heavy equipment to the river last year.

“We’re using data, science and advice from a wide range of agencies, including citizen groups along the river,” she said. “That’s the only way to carry out a project this big.”

The nutrient enrichment project also was preceded by at least five years of study before the first dose of fertilizer was trickled into the river in 2005.

Since water cannot be released from low levels of Libby Dam, most of the river’s phosphorous apparently settles behind the dam on the bottom of Lake Koocanusa.

Nutrients that get through the dam are used up by aquatic life in the Montana stretch, where trout populations have been less impacted by the dam.

“By the time the water gets to Idaho, life in the river has used up all the nutrients,” said Ryan Hardy, Idaho Fish and Game Department fisheries biologist.

Hardy and Holderman, both of whom have been working on the nutrient project since around 2001, say adding $50,000 of nutrients a year to the river near the state line has been successful. The fertilizer, mostly phosphorous, provides more food for the algae that nourish the aquatic insects that feed the fish and birds along the river.

The liquid fertilizer is trickled into the river in precise amounts from June through September, the general growing season for algae. Monitoring assures the mix is not having detrimental impacts on the aquatic ecosystem.

“It’s worked very well and we’re going to ask for funding to do it another five years,” Holderman said. “Unless we find another way of getting nutrients around the dam, and that’s not likely, this is the way to go.”

“Not only are the fish fatter,” Hardy said, “they’re healthier more fecund fish that produce more eggs and have better overwinter survival.

“Before Libby Dam was built, surveys indicate the Kootenai had about 3,500 aquatic insects per meter squared,” he said. “After the dam, the average was around 800 in the same Idaho waters. In five years of adding nutrients, insects have increased four- to five-fold.”

Fish have responded to the beefed up smorgasbord.

The mountain whitefish population in roughly a mile section of the river was down to 4,000-6,000 fish in the 1990s, he said. After three years of adding nutrients, the number of fish had grown to 14,000-17,000 – almost to pre-dam levels.

To boost the effort starting in 2002, Idaho changed the daily trout bag limit from six fish of any size to only two fish, none less than 16 inches.

“The trout population in the late ’90s above Bonners Ferry was around 50 fish per kilometer,” Hardy said. “After the regulations change the density went up to around 100 fish per kilometer. Following fertilization we saw it double to around 200 fish per kilometer.”

For comparison, trout populations on the angler-prized St. Joe and North Fork Coeur d’Alene rivers are 400-600 fish per kilometer, he said.

Kootenai River angler creel surveys showed that catch rates increased from 0.37 trout per hour in 2005 to 0.66 per hour in 2010.

“Surveys show that anglers rate their fishing experience really good and enjoyable when the catch rate is at least one fish per hour,” Hardy said. “So we’re pleased with the 10-fold improvement, but we still have a ways to go.

“We don’t see a lot of fish longer than 16 inches, so we have to figure out if that’s as big as these fish will get or what.

“We’ve been dealing with one limiting factor – the reduction in food availability caused by lower nutrients. We’ve found a remedy for that. Now we have to identify other limiting factors, such as limited spawning areas, habitat issues and genetics.”

As they work on improving the fishery, Idaho Fish and Game officials also are looking into improving angler access to the river.

The only good access points for floating the trout water in Idaho include a put-in near the Yaak River in Montana followed by a long float through the Kootenai’s canyon section to Twin Rivers Resort just east of the Moyie River.

Or floaters can put in at Twin Rivers and float through the braided section to the boat ramp downstream from the U.S. 95 bridge at Bonners Ferry.

“Most of the land along the river is private,” said Chip Corsi, IFG’s Panhandle Region manager. “Access is difficult, but we’re looking into it as much as we can.”